Oracle Message NNO-00709 - failed delete of cache checkpoint file string, cache flush may not work

ERROR	failed delete of cache checkpoint file string, cache flush may not work
CAUSE	the server attempted to flush its cache, which also deletes the cache checkpoint file. The file deletion failed, although the rest of the cache flush succeeded. Succeeding errors describe the reason for the deletion failure.
ACTION	This error typically occurs when two cache-flush operations are issued in succession without an intervening cache checkpoint operation (which would recreate the file). The first deletes the cache file, the second attempts to do so, but fails since the file has already been deleted. In such cases, the message is harmless and can be ignored. If, however, the error occurs because the server lacks permission to delete the file, then you must change the file system permissions so the server is allowed to delete the file.